The use of flexible film circuitry i.e., circuitry disposed on a thin insulating material such as polyimide polyester, or the like, to interconnect one circuit array with another array to provide a means to achieve extremely high density interconnections is known in the art. Flexible film circuitry is particularly suitable for use when dealing with dense arrays of circuits having closely spaced centerlines. The circuitry on the film is easily reconfigurable and the film provides a seamless extension from the mother board to a daughter card.
U.S. Pat. No. 3,922,054 discloses one early use of flexible film with a zero insertion force (ZIF) card edge connector in which a flexible circuit is looped around a channel and held taught against it by retaining it. The circuits wrapped around the spring portions are brought into contact with corresponding circuits on the daughter card by means of cams.
Other more recent ZIF type connectors are disclosed in U.S. Pat. No. 4,911,643 in which the camming action is provided by a shape-memory alloy that is activated by an electrical circuit; and U.S. Pat. No. 5,308,257 that uses a camming slide member.
U.S. Pat. No. 5,195,897 discloses a two-piece connector using flexible film circuitry in which the film is wrapped around a C-shaped spring member. The spring member is spread apart prior to engaging a circuit board by cam bearing surfaces on sidewalls of a support structure associated with the circuit board. A handle attached to the C-shaped spring member provides means for disconnecting the member from its associated circuit board.
The use of a camming type mechanism however increases the complexity of the connector as well as the associated manufacturing cost. In addition, the camming mechanism generally occupies space on the board and at a minimum requires that there be sufficient room surrounding the connector to permit access to it in order to activate the mechanism to permit insertion and withdrawal of the daughter cards. It is desirable, therefore, to have a surface mountable card edge connector using flexible circuitry that does not require the use of a camming mechanism whether mechanically, electrically, or otherwise activated, thereby conserving board space and permitting closer stacking of daughter cards.